Interferometric synthetic aperture radiometers have been developed to obtain a high angular resolution using a static array of small antennas, avoiding the scanning of the large size antenna required by real aperture radiometer. An imaging system using a synthetic aperture radiometer reconstructs an image by receiving a radiant energy naturally emitted from an object on the ground in a micrometer-wave or a millimeter-wave band via an antenna array. In this radiometer imaging system, the structure of the antenna array is an important fact that determines acquisition efficiency for image. In general, the antenna array employed in the radiometer imaging system has a pattern in which an overall arrangement is in a Y-type, a Δ-type or a T-type. Among a variety of antenna array patterns, it is well known that the Y-type antenna array is capable of obtaining a narrow width of synthetic aperture beamwidth and a wide range of alias free FOV (Field Of View)
In a conventional Y-type antenna array, however, a number of antenna elements are required to obtain a high resolution image. For example, 130 or more antenna elements are needed to obtain a synthetic aperture beamwidth of about 1°. However, with the increase of the antenna elements, the structure of an overall antenna array becomes complicated, and an operation calculation for obtaining correlations between signals received from each pairs of the antenna elements becomes difficult, which results in an increase of power consumption and a demand for a large-scale system.
Further, in the high resolution imaging system, spatial frequency sampling is performed using the relative distance difference between antenna elements. However, visibility functions in visibility coverage are not sampled in a spatial frequency domain to introduce the alias effect, which is one of the factors deteriorating the image quality recovered by the imaging system.